Thursday, May 26, 2011

High dynamic range imaging (HDRI or just HDR) is a set of techniques that allow a greater dynamic range of luminance between the lightest and darkest areas of an image than current standard digital imaging techniques or photographic methods. This wide dynamic range allows HDR images to more accurately represent the range of intensity levels found in real scenes, ranging from direct sunlight to faint starlight.

In short, camera processors are dumb. They can't process light and colours as our eyes and brain functions. In times with high dynamic range, such as area with great light and darkeness together, it is very hard for the camera to snap a picture with normal exposure. Thus, HDR imaging come in place.

HDR imaging involves taking few photos with different exposure values (EV), normally -2, 0 and +2. Next, you can either uses image processing software like Adobe Photoshop or Photomatrix to combine the photos together. With some tone-mapping, the results can be interesting.

For examples,A statue of God Monkey at Broga Temple. When we arrive, it was around 3pm with strong sun light. All shots on this statue are either sky overexposed (too bright) or the statue being too dark (underexposed). So I use exposure braketing and took three photos with exposure -2, 0 +2, combine using Photomatrix Pro 4.

From left top-bottom: EV-2, 0 +2 ; Right: HDR processed.The result is, a normal exposed photo. Brightened details of the statue from EV+2, sky with combination of EV 0 and EV-2.

Next, an example of area with high dynamic of both brightness and colour.

It was just lousy shots before processing. I can't even recognize why did i took these shots. After combination, it came out quite impressing, with the greeneries of the forest displayed, and the 'Jesus Light' nicely displayed.